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Bug in EEM SNMP event detector

Jared Valentine found an interesting bug in the EEM’s SNMP event detector: if you’re triggering your EEM applet when the increment of an SNMP variable exceeds the threshold, you cannot re-arm the applet; the exit-type increment does not work. He fixed the problem with a somewhat more convoluted approach:

  • The first EEM applet reads the SNMP variable, waits a second, does a second read and stores the difference in a counter.
  • The second EEM applet is triggered based on the counter values.

I’m collecting tips like this one in the Embedded Event Manager (EEM) workshop. You can attend an online version of the workshop; we can also organize a dedicated event for your networking team.

Here’s the source code for the first applet (he had to execute CLI show commands to work around the CB-QoS MIB limitations).

event manager applet AATQoS
 event timer watchdog time 1
 action 100 cli command "enable"
 action 110 cli command "show policy-map int dialer0"
 action 200 info type snmp oid cbQosCMPrePolicyByte.368.13007857 →
  get-type exact community public
 action 210 set value1 "$_info_snmp_value"
 action 220 wait 1
 action 300 cli command "show policy-map int dialer0"
 action 310 info type snmp oid cbQosCMPrePolicyByte.368.13007857 →
  get-type exact community public
 action 320 set value2 "$_info_snmp_value"
 action 400 subtract $value2 $value1
 action 410 counter name "qos_delta" op set value $_result

1 comment:

  1. Not sure if my issue is related to this. I had an issue with EEM SNMP detector on. It failed to work after a few days. I had to remove all the event manager applet and reconfigure them to get it working again.

    I tried the same config on both 4500 and 3560 switches. Same problem. :(


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Ivan Pepelnjak, CCIE#1354 Emeritus, is an independent network architect. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or follow @ioshints on Twitter.